The aspects of the disclosed embodiments pertain to the field of transport aircraft. More specifically, the aspects of the disclosed embodiments concern an aircraft with a wing positioned above the fuselage with the ability to move the wing in flight relative to the fuselage.
In a broadly expanded aerodynamic architecture corresponding to the great majority of modern aircraft in particular for transport aircraft, the aircraft has a fuselage of generally elongated shape to which a wing is attached in a central part of the fuselage along its length and to which a set of airfoils is attached, including a vertical airfoil or V-tail and a horizontal airfoil or stabilizer intended to assure the aerodynamic stability of the aircraft in flight and its control using flaps of the airfoils.
The aircraft also has one or more engines that are mounted on the wing or fuselage, depending on the case. In such designs, the wing, which is generally of separate form from the fuselage, is mounted on the fuselage. The wing may be mounted on a lower part of the fuselage, e.g., in the case of an aircraft of the Airbus A320 type, on an upper part of the fuselage, e.g., on an aircraft of the ATR72 type, or following a less common configuration for transport aircraft, in a position of intermediate height, as in the case of the Breguet 765 aircraft.
In all of these examples of an aircraft representative of the most widely used transport aircraft, the wing is fixed to the fuselage so as to be held in a fixed position and to transmit to the fuselage structure all of the aerodynamic forces, propulsive forces and inertial forces that are encountered during flight. Numerous technical designs have been created and are used to realize the structural junction between the fuselage and the wing.
According to a specific engineering design applied to certain aircraft whose wing is above the fuselage, the wing is attached to the fuselage using forks and connecting rods assuring the transmission of forces.
The designs for static fixation of a wing to a fuselage are advantageous from the standpoint of the structural design, in particular with respect to the ratio of the weight of the fixation means to the forces transmitted, but they also require the designer of the aircraft to determine the average values of the wing positions, in particular, an angular setting relative to a reference fuselage and a longitudinal position on the fuselage, which are compromises and are only optimal for one or a few conditions of flight. Furthermore, the aircraft designer determines the longitudinal position of the wing on the fuselage in order to comply with the restricted positions of the center of gravity, and this further requires controlling the center of gravity as a function of this choice with no further action possible.
The designer also determines the setting angle of the wing, i.e. an angle of incidence of a reference profile of the wing relative to the axis of the fuselage, generally in order to assure an essentially horizontal position of the axis of the fuselage for an average cruising weight in order to minimize the aerodynamic drag of the fuselage and to benefit from an essentially horizontal floor of the cabin for the comfort of the passengers. However, outside of the conditions of flight (weight, speed and altitude), which resulted in the determining of the wing setting, in general the fuselage has neither a zero aerodynamic incidence nor a horizontal floor.
Some aircraft have a wing that is mobile relative to the fuselage when in flight. However, the movements of the wing of such aircraft are confined to the capacity of the wing to pivot around a fixed axis relative to the fuselage and have essentially only been used in experimental aircraft.
For example, the wing pivots to cause the setting angle to vary around a value close to the mean value in order to regulate the setting angle or, more frequently, to achieve attitude control by direct action on the wing angle of attack. The number of solutions conceived on this principle is relatively large, e.g., the “pou du ciel” design developed by Henry Mignet, a description of which is given in the patent GB 455 462. Although providing a partial answer to the problem of optimal wing angular setting as a function of the conditions of flight, the solution proposed of rotation of the wing around an axis under the influence of an actuator has not resulted in sufficient advantages to be implemented in transport aircraft.
For example, the wing pivoted to vary the angle of incidence up to a value of 90.degree in order to orient the thrust of the engines (or propellers) upward and permit a vertical takeoff and then take back a low angle of incidence close to 0.degree. for conventional cruising flight as in the Veserflug P1003 design or on the experimental aircraft Canadair CL84. This mobile wing solution, an example of which is described in the patent application GB 907 590, has a very specific objective and does not appear to be of use for improving the situation of transport aircraft.
For example, the wing pivoting, about a vertical axis in the reference axis system of the aircraft, at the level of the fuselage in order to vary the sweep of the wing anti-symmetrically to adapt the wing to the Mach number of flight with a configuration called oblique wing. This type of mobile wing as in the Messerschmidt P202 design and tested in flight on the NASA experimental aircraft ADI only provides a solution to the problem of adaptation of the two-dimensional shape of the wing to the speed of flight and has been the subject of research as an alternative solution to variable swept-wing aircraft, a heavy, costly solution and the source of numerous technical difficulties that has only found application on armed military aircraft.